I tried an experiment to see if UV LEDs would work to expose cyanotype sensitised paper, turns out they do. I used three puny standard LEDs, first within a centimeter of the paper to make sure something happened, after about five minutes they had left some good amber splodges. Then I set it up like this with the LEDs about 30cms from the paper and part of a floppy drive motor (probably) to leave an interesting pattern, left for about an hour. See the next picture for the result.
I’ll be getting hold of a 10W UV LED soon. This should make unreliable sunny days much less of a problem.

BuildBrighton - Brighton’s Hackerspace ran its badge making and "soldering is easy" workshop last weekend.
The workshop involved soldering together badges consisting of an RGB LED, a microcontroller, battery, IR LED and IR receiver. The badges have a unique ID which is represented as a colour on the LED. They constantly transmit their ID using IR, other badges can receive the transmissions and collect colours which they cycle through on the RGB LED. They also have a zombie game mode where a badge can become "infected" and flashes red. It will then infect all other badges that receive its transmissions.